package org.xiaov.core.string;

/**
 * <p>
 *
 * </p>
 *
 * @author xiaovcloud
 * @since 2021/8/22 上午11:14
 */
public class HexHelper {
	private static final char[] DIGITS_LOWER = {'0', '1', '2', '3', '4', '5',
			'6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
	private static final char[] DIGITS_UPPER = {'0', '1', '2', '3', '4', '5',
			'6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

	/**
	 * 16进制转byte数组
	 *
	 * @param data 16进制字符串
	 * @return byte数组
	 * @throws Exception 转化失败的异常
	 */
	public static byte[] hex2Bytes(final String data) throws Exception {
		final int len = data.length();

		int num = 0x01;
		if ((len & num) != 0) {
			throw new Exception("Odd number of characters.");
		}

		final byte[] out = new byte[len >> 1];

		// two characters form the hex value.
		for (int i = 0, j = 0; j < len; i++) {
			int f = toDigit(data.charAt(j), j) << 4;
			j++;
			f = f | toDigit(data.charAt(j), j);
			j++;
			out[i] = (byte) (f & 0xFF);
		}
		return out;
	}

	/**
	 * bytes数组转16进制String
	 *
	 * @param data bytes数组
	 * @return 转化结果
	 */
	public static String bytes2Hex(final byte[] data) {
		return bytes2Hex(data, true);
	}

	/**
	 * bytes数组转16进制String
	 *
	 * @param data        bytes数组
	 * @param toLowerCase 是否小写
	 * @return 转化结果
	 */
	public static String bytes2Hex(final byte[] data, final boolean toLowerCase) {
		return bytes2Hex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
	}


	/**
	 * bytes数组转16进制String
	 *
	 * @param data     bytes数组
	 * @param toDigits DIGITS_LOWER或DIGITS_UPPER
	 * @return 转化结果
	 */
	private static String bytes2Hex(final byte[] data, final char[] toDigits) {
		final int l = data.length;
		final char[] out = new char[l << 1];
		// two characters form the hex value.
		for (int i = 0, j = 0; i < l; i++) {
			out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
			out[j++] = toDigits[0x0F & data[i]];
		}
		return new String(out);
	}

	/**
	 * 16转化为数字
	 *
	 * @param ch    16进制
	 * @param index 索引
	 * @return 转化结果
	 * @throws Exception 转化失败异常
	 */
	private static int toDigit(final char ch, final int index)
			throws Exception {
		final int digit = Character.digit(ch, 16);
		if (digit == -1) {
			throw new Exception("Illegal hexadecimal character " + ch
					+ " at index " + index);
		}
		return digit;
	}

}
